As it seems that no one has responded yet, I would think that you could add fatheads into the water through the ice, however, I would think that they would be naturally disoriented so much so that they would be the proverbial "deer in the headlights" and make for easy prey.

I would think that you might have more success of some survival by putting them in an secured area where they could have some acclimation time without Ole Wally eying them down.

There was some other discussions on the forum of how forage fish did better in warm water stockings when they had a chance to acclimate, in the pond, for several hours without the threat of predation.

If you were just putting the fatheads in for easy, rapid meals for the walleyes, then I would go for it.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."